CN102866134B - Optical system for laser-induced detection - Google Patents

Abstract

The present invention relates to a laser introduction optical system of a novel laser-induced detection device, in particular to a method for converging laser light on the surface of a substance to be detected, obtaining the composition of the material to be detected through the plasma spectrum excited by the laser, or using the laser to detect the composition of the material inside the material And the ultrasound excited by the surface is analyzed to obtain the laser introduction optical system of the internal defect of the material, which belongs to the field of laser induced detection. The system involved in the present invention includes: an outer sleeve, a beam splitting prism, a beam splitting baffle, a beam selection baffle, and a focusing sleeve. The focusing sleeve can also be replaced with a reflector group, or an electric controller can be added, or a focus can be added. lens. In the present invention, the method of splitting the laser beams and controlling the energy of a single laser beam to be below the threshold of the induced excitation, and above the excitation threshold when the multiple beams are merged, realizes the induced adjustment control, and can simultaneously avoid focusing the laser on the induced excitation threshold. Detects problems that are on the material, or cause gas breakdown.

Description

An optical system for laser-induced detection

technical field

The present invention relates to a new type of laser induction optical system of a laser induction detection device, in particular to a method of converging laser light on the surface of a substance to be detected, and obtaining the composition of the material to be detected through the plasma spectrum excited by the laser, or through the laser light inside the material And the ultrasound excited by the surface is analyzed to obtain the laser introduction optical system of the internal defect of the material, which belongs to the field of laser induced detection.

Background technique

Laser-induced plasma spectroscopy (Laser Induced Plasma Spectroscopy, LIPS) detection technology is an analytical technique that uses pulsed laser ablation of substances to generate plasma, and qualitatively or quantitatively studies the composition of substances through plasma emission spectra. It has the advantages of wide application range, fast analysis speed, less destructive measurement, remote non-contact measurement and real-time detection. Laser-induced plasma spectroscopy is a quantitative analysis technique based on the emission spectrum generated by the interaction between laser and material. This method only needs a few micrograms in the measurement process, which can realize non-destructive measurement and can realize the analysis without sample pretreatment. Elemental analysis of substances in any physical state. Laser-induced plasma spectroscopy can quantitatively analyze the elements in substances through calibration, and the detection limit and precision fully meet the application requirements, and has been widely used in many fields.

On the other hand, laser-induced ultrasonic testing technology is a non-destructive testing technology that uses laser to excite and detect ultrasound. After the laser is focused on the surface of the material to be tested, the irradiated material will expand, forming a thermoelastic effect or ablation. The thermoelastic effect or the ablation effect can excite the ultrasonic wave with the laser irradiation point as the source. Compared with the traditional piezoelectric ultrasonic testing technology, the laser-induced ultrasonic testing technology has the advantages of non-contact, broadband, and point emission and reception. Therefore, laser-induced ultrasonic testing technology can be applied in material characterization, defect detection, process monitoring, and detection or monitoring of workpieces with complex shapes or equipment in special environments such as high temperature, high pressure, corrosion, and radiation.

At present, there are some patents at home and abroad that have protected this aspect, such as the laser ultrasonic nondestructive testing device with the application number 200780101871.0. After the laser is focused on the material through the lens, it can be folded and advanced to realize the scanning detection of a large area. The patent application No. US2003/0172736A1 introduces a laser-induced ultrasonic detection system using an optical fiber structure. The system integrates the laser-induced ultrasonic excitation source and the laser-induced ultrasonic detection signal lens coaxially to achieve detection. US patent US7671349B2 protects a laser-induced plasma device, which uses a collection structure including a concave mirror to focus the laser light on the detected substance, which is compact and practical.

Both laser-induced plasma spectroscopy and laser-induced ultrasonic testing require an optical system to focus the laser on the surface of the material to be tested for laser induction. The induced laser is usually focused by a lens. The biggest problem faced by this method is that the focus size is relatively small. Once the distance between the material to be tested and the focusing lens fluctuates, it will affect the implementation of the test. For laser-induced plasma spectroscopy, when the focus is on the surface of the material, gas breakdown occurs, so that the monitored spectrum is the air spectrum instead of the spectrum of the material to be detected; for laser-induced ultrasonic detection technology, when the induced laser When it happens to converge on the surface of the material, damage occurs and destroys the inspected part.

Contents of the invention

The purpose of the present invention is to provide a new optical introduction system in the laser-induced detection technology, which is used to solve the problem of laser-induced adjustment in the implementation process of the laser-induced plasma spectroscopy technology and the laser-induced ultrasonic detection technology. In the present invention, the method of splitting the laser beams and controlling the energy of a single laser beam to be below the threshold of the induced excitation, and above the excitation threshold when the multiple beams are merged, realizes the induced adjustment control, and can simultaneously avoid focusing the laser on the induced excitation threshold. Detects problems on materials, or that cause gas breakdown.

The purpose of the present invention is achieved like this:

The optical system for laser-induced detection involved in the present invention, as shown in Figure 1 and Figure 2, includes: an outer sleeve 1, a beam splitting prism 2, a beam splitting baffle 3, a beam selection baffle 4, and a focusing sleeve 5, It is also possible to replace the focusing sleeve 5 with a mirror group 6 , or add an electric controller 7 , or add a focusing lens group 8 .

In the described technical solution, the outer sleeve 1 is used to focus the induced excitation laser beam on the surface of the material to be detected;

In the described technical solution, the described dichroic prism 2 is used to disperse the inductive incident laser light into multiple beams;

In the described technical solution, the described spectroscopic baffle 3 is used to pass through the beam-split laser light and block the laser light reflected by the beam selection baffle 4 to avoid scattering interference;

In the described technical solution, the beam selection baffle 4 is used to select the incident multiple beams of laser light, and control part or all of them to pass through;

In the described technical solution, the inner wall of the focusing sleeve 5 can be a prism surface, a circular mesa surface or a combined curved surface, which is made of metal polishing or other material coatings, and is used to reflect and change the direction of multiple induced laser beams, so that Multiple induced laser beams converge on one surface.

In the above technical solution, the reflector group 6 can be made of polished metal or coated with glass and other materials, and can be flat or concave or convex, and has the same function as the focusing sleeve 5 .

In the technical solution, the electric controller 7 includes a driving motor and a transmission mechanism, which are used to realize the electric control of the beam splitting baffle 3 , the beam selection baffle 4 , and the focusing sleeve 5 .

In the described technical solution, the focusing lens group 8 can be added in front of the dichroic prism 2, between the dichroic prism 2 and the dichroic baffle 3, between the dichroic baffle 3 and the beam selection baffle 4, the beam selection Between the baffle plate 4 and the focusing sleeve 5, it is used to realize the convergence of a single beam of light.

Compared with the prior art, the present invention has the following advantages:

Whether it is laser-induced plasma spectroscopy detection technology or laser-induced ultrasonic detection technology, it is necessary to focus the laser on the surface of the tested part for excitation. The existing excitation technology uses a lens to focus the laser on the surface of the material to achieve high energy density excitation, but there are problems of air breakdown and precise positioning of the focus. The present invention avoids the existence of the focal point of the lens, and realizes the induction laser induction through the overlapping of multiple laser beams, so that the position of the focus point is unclear, and the gas breakdown of the induction laser and the damage of the detected material can be effectively avoided.

Description of drawings

Figure 1 is a cross-sectional view of an optical system for laser-induced detection.

Fig. 2 is an external view of an optical system for laser-induced detection.

Figure 3 is the internal structure of the optical system used for laser-induced detection.

Fig. 4 is an example of another internal structure scheme of an optical system for laser-induced detection.

Fig. 5 is a structural diagram of a 90-degree four-piece one-layer beam splitting prism used in the optical system for laser-induced detection.

Fig. 6 is a structural diagram of a 4-beam splitting shading plate of an optical system for laser-induced detection.

Fig. 7 is a structural diagram of a beam selection baffle for an optical system for laser-induced detection.

Fig. 8 is a structural diagram of a 45-degree 8-block one-layer dichroic prism used in the optical system for laser-induced detection.

Fig. 9 is a structural diagram of a 45-degree 8-block two-layer beam splitting prism used in the optical system for laser-induced detection.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments.

Example 1

Referring to Figure 1, Figure 2, and Figure 3, fabricate an optical system for laser-induced detection. The outer sleeve 1 is made of welded stainless steel, and the inside is a threaded structure, and the optical element is tightened and fixed by a metal ring containing external threads. Along the light passing sequence, the first optical element is the focusing lens group 8, and the second optical element is the beam splitter 2, which is used to disperse the incident laser light for induction into 4 beams. The structure is shown in Figure 5. The third optical element is the beam-splitting baffle 3, which is made of an aluminum sheet with a thickness of 1 mm. It contains four light holes with a diameter of 3 mm, which form a circular array at an angle of 90°. The structure is shown in Figure 6. The light is emitted through these 4 light holes. The fourth optical element is the beam selection baffle 4, on which 12 holes are arranged along a circle, the structure is shown in Figure 7, by rotating the beam selection baffle 4, 1, 2, 3, 4 laser beams can be selected through the beam Baffle 4. The laser light blocked by the beam selection barrier 4 is scattered between the beam selection barrier 4 and the beam splitting barrier 3 . The fifth optical element is the focusing sleeve 5, the inner wall of which is a circular frustum surface, and is made of metal aluminum polished and plated with a high-reflection film. detection surface. On the outside of the outer sleeve 1, an electric controller 7 is attached, which is used to adjust the beam splitting baffle 3 and the beam selection baffle 4 through an external control signal, so as to realize electric control of laser light splitting.

Example 2

Referring to Figure 4, fabricate an optical system for laser-induced detection. The outer sleeve 1 is made of aluminum plate, the inside is a sliding sleeve structure, and each element has a sleeve outside. The positioning of the optics is achieved by tightening the screws. Along the light passing sequence, the first optical element is the beam splitter 2, which is used to disperse the incident laser light for induction into 8 beams, as shown in Figure 8. The second optical element is the beam-splitting baffle 3, which is made of a steel sheet with a thickness of 0.5 mm and contains 8 light holes with a diameter of 5 mm. The light split by the beam-splitting prism 2 is emitted through the 8 light holes. The third optical element is the beam selection baffle 4, on which 20 holes are arranged in an array with equal angular spacing along a circle with a diameter of 50 mm. By rotating the beam selection baffle 4, 2, 4, 6, and 8 laser beams can pass through the beam Select bezel 4. The laser light blocked by the beam selection barrier 4 is scattered between the beam selection barrier 4 and the beam splitting barrier 3 . The fourth optical element is the focusing sleeve 5, the inner wall of which is equipped with reflector group 6, the reflector is circular with a diameter of 10mm. The laser beams transmitted through the beam selection baffle 4 are redirected by the mirror group 6 and collectively converged on the surface to be detected. When in use, by manually controlling the angle of the beam selection baffle 4, multiple laser beams can be irradiated on the material surface to realize laser-induced excitation.

Example 3

Referring to Figure 4, fabricate an optical system for laser-induced detection. The outer sleeve 1 is made of aluminum plate, the inside is a sliding sleeve structure, and each element has a sleeve outside. The positioning of the optics is achieved by tightening the screws. Along the light passing sequence, the first optical element is the beam splitter prism 2, which is used to disperse the incident laser light for induction into two layers, each layer has 8 beams, as shown in Figure 9. The second optical element is the beam-splitting baffle plate 3, which is made of a steel sheet with a thickness of 1 mm. It contains two layers of 8 light holes with a diameter of 3 mm on each layer. The light split by the beam-splitting prism 2 passes through these 8 light holes. shoot out. The third optical element is the beam selection baffle 4, which is divided into two layers along a circle with a diameter of 50 mm at equal angular intervals, and each layer is arrayed with 20 holes. By rotating the beam selection baffle 4, 4, 8, and 12 holes can be realized. 16 laser beams pass through the beam selection baffle 4 . The laser light blocked by the beam selection barrier 4 is scattered between the beam selection barrier 4 and the beam splitting barrier 3 . The fourth optical element is the focusing sleeve 5, the inner wall of which is equipped with reflector group 6, the reflector is circular with a diameter of 10mm. The laser beams transmitted through the beam selection baffle 4 are redirected by the mirror group 6 and collectively converged on the surface to be detected. When in use, by manually controlling the angle of the beam selection baffle 4, multiple laser beams can be irradiated on the material surface to realize laser-induced excitation.

Claims (7)

1. An optical system for laser-induced detection, comprising: an outer sleeve (1), a beam-splitting prism (2), a beam-splitting baffle (3), a beam selection baffle (4), and a focusing sleeve (5) , it is also possible to replace the focusing sleeve (5) with a mirror group (6), or increase an electric controller (7), or increase a focusing lens group (8); The outer sleeve (1) is used to converge the induced excitation laser beam on the surface of the material to be detected; the described beam splitting prism (2) is used to disperse the induced incident laser beam into multiple beams; the described The beam splitting baffle (3) is used to pass through the beam splitted laser light, and to block the laser light reflected by the beam selection baffle (4) to avoid scattering interference; the beam selection baffle (4) is used to treat the incident multiple beam The laser is selected, and part or all of it is controlled to pass through; the focusing sleeve (5) is used to reflect and change the direction of multiple induced laser beams, so that multiple induced laser beams are collectively converged on one surface; the described The reflector group (6) can be made of materials such as metal polishing or glass coating, which can be flat or concave or convex, and has the same function as the focusing sleeve (5); the electric controller (7) includes a drive The motor and the transmission mechanism are used to realize the electric control of the beam splitting baffle (3), the light beam selection baffle (4), and the focusing sleeve (5); the focusing lens (8) can be added to the beam splitting prism (2 ) or between the beam splitting prism (2) and the beam splitting baffle (3) or between the beam splitting baffle (3) and the beam selection baffle (4) or between the beam selection baffle (4) and the condenser sleeve (5) , used to realize the convergence of a single beam of light. 2. The optical system for laser-induced detection according to claim 1, characterized in that the beam splitting prism (2) is used to realize the splitting of the laser light, which can be divided into 1 to 50 equal parts along the axial direction, each It is fan-shaped; it can also be a combination of 1 to 50 equal divisions along the radial direction and 1 to 50 equal divisions along the axial direction, dividing the beam into 1 to 50 rings along the same center of the circle, and performing 1 to 50 equal divisions. 3. The optical system for laser-induced detection according to claim 1, characterized in that, the included spectroscopic baffle (3) and beam selection baffle (4) are used to realize the selection of light beam transmission, and in the spectroscopic shading The plate (3) and the beam selection baffle (4) can be provided with light splitting holes along one or up to 10 circumferences, and can contain 1 to 100 holes on each circumference, and the spacing of these holes is not equal, mainly The purpose is to cooperate with the holes on the beam splitting baffle (3) and the beam selection baffle (4) to achieve different sets of laser light transmission, and the shape of each hole can be circular, rectangular, trapezoidal or fan-shaped, usually with a diameter of Round holes from 1 to 20mm or rectangles with a side length from 1 to 20mm. 4. The optical system for laser-induced detection according to claim 1, characterized in that, the light-gathering sleeve (5) included is used to realize the convergence of the separated light beams, and the inner wall can be a prism table, a circular table or The combined curved surface is composed of metal polishing or plastic, glass, and ceramics plated with high-reflection film; the concentrating sleeve (5) can be formed by surrounding and pasting 3 to 30 trapezoidal lenses, and can be made of aluminum, iron, and copper through mechanical processing. The hole constituting the inner cavity can be in the shape of a cylindrical hole, a truncated truncated hole, or a combination of a spherical surface, a cylinder and a truncated truncated hole. 5. The optical system for laser-induced detection according to claim 1, characterized in that, the focusing sleeve (5) can also be replaced with a reflector group (6), and the reflectors from 1 to 50 are in accordance with appropriate These mirrors can be metal mirrors, ceramics, glass mirrors, and the mirrors can be circular, rectangular or trapezoidal; the reflective surface of the mirror can be flat, concave or convex, or spherical It can also be aspherical. 6. The optical system for laser-induced detection according to claim 1, characterized in that, a focusing lens group (8) can be added in front of or behind the focusing sleeve (5) to realize further focusing of multiple beams of light. Convergence, and the precise positioning of the beam convergence position through the adjustment of the focusing lens group (8); the focusing lens group (8) can be added with an electric control system to achieve automatic adjustment, or through manual adjustment. 7. The optical system for laser-induced detection according to claim 1, characterized in that, behind the beam splitting prism (2) and before the beam splitting shield (3), a focusing lens group can be added to realize multi-beam light Further convergence, and the precise positioning of the beam convergence position can be realized by adjusting the focusing lens group (8); the focusing lens group (8) can be added with an electric control system to realize automatic adjustment, or through manual adjustment.